ChemInform Abstract: Ag-Catalyzed Diastereo- and Enantioselective Synthesis of β-Substituted Tryptophans from Sulfonylindoles.

ArticleinOrganic Letters 12(8):1688-91 · March 2010with9 Reads
DOI: 10.1021/ol100161n · Source: PubMed
Abstract
The asymmetric catalytic synthesis of beta-substituted tryptophan derivatives was realized in high diastereo- and enantioselectivity by the reaction of glycine derivatives with sulfonylindoles in the presence of catalyst derived from AgCl and a commercially available chiral monodentate phosphoramidite ligand. The resulting adduct was readily converted to beta-substituted tryptophan in 95% overall yield for two steps, which presented a highly efficient route to chiral beta-substituted tryptophan.
    • "On the other hand, non-racemic tryptophan derivatives were prepared with moderate stereoselectivities by F–C alkylation when ΔAla was incorporated into peptides (Gentilucci et al. 2010). Some asymmetric catalytic syntheses have been reported to afford with high levels of enantioselectivity (S)or (R)-tryptophans carrying a limited number of distinct modifications (Drury et al. 1998; Castle and Srikanth 2003; Zheng et al. 2010). Heck reaction between N-Ts-indoles and methyl 2-acetamidoacrylate furnished the dehydrotryptophans , whose asymmetric catalytic hydrogenation with [(COD)Rh(Et-DuPHOS] + TfO − as catalyst furnished enantiomerically pure (R)-5-and 6-substituted tryptophans (Prieto et al. 2009). "
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